executioner vs hangman

executioner and hangman both are nouns.

Word	Noun	Adjective	Verb	Adverb
executioner	Yes	No	No	No
hangman	Yes	No	No	No

As nouns, hangman is a hyponym of executioner; that is, hangman is a word with a more specific, narrower meaning than executioner:

executioner: an official who inflicts capital punishment in pursuit of a warrant
hangman: an executioner who hangs the condemned person

Other hyponyms of executioner include electrocutioner, headman, headsman.

executioner (noun)	hangman (noun)
an official who inflicts capital punishment in pursuit of a warrant	an executioner who hangs the condemned person